Despite a rather large formulary of antihistaminic drugs used in medical practice as antiallergic agents, the search for new H-1 histamine receptor blockers remains an urgent task, inasmuch as most existing preparations of this class have deficiencies, such as short duration of action, the presence of side effects on the central nervous system, and so forth. (M. D. Mashkovsky, Lekarstvennye sredstva [Medications], Moscow, Novaya volna, 2005, 15th edition, pp. 285-297). In this regard, the search for original antihistamine (antiallergic) medications with a novel chemical structure is of special interest, and, in particular, the xanthine derivatives series, among which are a number of highly active natural compounds (theophylline, theobromine, caffeine) with valuable pharmacotherapeutic properties.